This project is directed towards an investigation of various factors involved in the control of steroid hormone synthesis in the different zones of the adrenal cortex. In particular the mechanism of action of ACTH will be studied and an assay system devised for the measurement of the labile factor produced in the presence of this tropic hormone in inner zones of the adrenal cortex. By taking advantage of the cholesterol-binding properties of this factor, affinity columns will be used to isolate and purify the factor. The eventual aim of these studies is to determine the structure of this factor which enables cholesterol to bind to side chain cleavage cytochorme P-450 in the adrenal and overcome the rate-limiting step of corticosteroidogenesis. We also propose to investigate the control of steroidogenesis in ACTH dependent and independent tumors of the adrenal cortex. In related studies the effects of ACTH, potassium, sodium and angiotensin II on the mitochondrial cytochrome P-450 systems of zona glomerulosa cells of the adrenal cortex will be investigated. Parallel studies will be made of the effects of these factors on the late pathway for aldosterone synthesis. In order to measure the interrelationships between zona glomerulosa and zona fasciculata-reticularis mineralocorticoid secretion, we propose to neutralize DOC, 18-hydroxy-DOC and aldosterone by active immunization with suitable steroid-protein conjugates and follow the effects on blood levels of these compounds.